EVOLUTION OF THE MULTI-TUBULIN HYPOTHESIS

Microtubules are organized into diverse cellular structures in multice llular organisms. How is such diversity generated? Although highly con served overall, variable regions within alpha- and beta-tubulins show divergence from other alpha- and beta-tubulins in the same species, bu t show conservation among different species. Such conservation raises the question of whether diversity in tubulin structure mediates divers ity in microtubule organization. Recent studies probing the function o f P-tubulin isotypes in axonemes of insects((1)) suggest that tubulin structure, through interactions with extrinsic proteins, can direct th e architecture and supramolecular organization of microtubules.